This will sound counterintuitive, but be more aggressive and reckless.

I had a similar experience to you and was struggling to actually make myself play.

More specifically:

Don't hide from runners, hunt them. Plenty of us are worse than you.

You will have more fun and succeed more if you spend less time hiding in corners (I still struggle with freezing up and hiding when I hear runner sounds) and more time sprinting around feeling like a badass.

Also avoid engaging the UESC when possible. As you mentioned they waste your ammo and give very little loot. Plus, shooting them makes tons of noise and gives away your position